Semi-automatic device for stuffing foodstuff into tubular nettings

ABSTRACT

In apparatus for semi-automatically stuffing foodstuff into tubular netting and continuously gathering netting about a tubular element, the action of centering, holding on position and aligning of the tubular element is combined with the netunwinding from spool-feeders in one single improved device which consists of a plurality of rolls located on the tubular element near a constricted section thereof. The tubular element, furthermore, may be removable, and when it is, the tubular element is contained within a sheath and supported therein by an axial spine with a plurality of spaced annuli. Several modifications of this concept are described and claimed, the concept being applicable to Apparatus of both the reciprocating and continuous net-gathering type.

United States Patent [191 Cherio et al.

[ Apr. 23, 1974 McMillan 53/258 X [5 SEMI-AUTOMATIC DEVICE FOR 3,555,775 1/1971 STUFFING FOQDSTUFF INTO TUBULAR 3/ sBartore et a1. 53/197 v I onaml X [76] Inventors: Vittoria Cherio; Giuseppe Mignone, Primary Examiner Travis SI McGehee both of vane San Matteo Assistant Examiner-John Sipos Cisterna dAsti, Italy [22] Filed: Apr. 17, 1972 57 ABSTRACT PP 244,433 In apparatus for semi-automatically stuffing foodstuff into tubular netting and continuously gathering netting [30] Foreign Application Priority Data about a tubular element, the action of centering, hold- N 7 1971 l l 709O0/71 mg on position and ahgnmg of the tubular element [S ta combined with the net-unwinding from spool-feeders in one single improved device which consists of a plu- CCll. 536645,b5;/9 rality of rolls located on the tubular element near a [58] i 258 constricted section thereof. The tubular element, furle 0 earc 1 thermore, may be removable, and when it is, the tubular element is contained within a sheath and supported therein by an axial spine with a plurality of spaced an- [56] References Cited nuli. Several modifications of this concept are de- UNITED STATES PATENTS scribed and claimed, the concept being applicable to 3,209,398 10/1965 Ziolko 17/42 Apparatus of both the reciprocating and continuous 3,461,484 8/l969 Al'llOld.... 17/42 X net-gathering type, 3,594,855 7/1971 Urbutis 17/42 3,561,192 2/1971 Soodalter 53/197 15 Claims, 29 Drawing Figures 7, 1 I 4 i 1 91 C 3 l" r .1 a I 1 .18 1

PATENTEDAPR 23 1974 SHEET 2 [1F 8 m wt w wt

Pmmmmzs 1914 3.805480 SHEET (if 8 PATENTEDAPRZB 1974 v I 8,805480 wmsms T ATENTED APR 2 3 I974 SHEET 8 BF 8 SEMI-AUTOMATIC DEVICE FOR STUFFING FOODSTUFF INTO TUBULAR NETTINGS FIELD OF THE INVENTION The present invention relates to a semi-automatic device for stuffing of foodstuff, especially roasts and the like, into tubular nettings and, further, it relates to the continuous gathering of the tubular netting upon the stuffing cylinder of the device.

BACKGROUND OF THE INVENTION There are already available processes for stuffing of foodstuff into tubular nettings, such foodstuff being, for example, roasts, salami, and other solid or paste-like foodstuff. These processes are generally carried out in one of two different manners and, specifically, either by stuffing the food product directly and using a length of netting equal to the length of finished stuffed product, or by gathering the netting about tubular rigid elements, within which the foodstuff is introduced. The foodstuff, in this latter process, is extruded from the tubular element and'drags a length of netting corresponding to the volume occupied by the foodstuff. To carry out either one of the two processes aforementioned, it is known to use suitable devices, such as those described in co-pending U. S. applications Ser. No. 208,179, filed on Dec. 15, 1971, now U.S. Pat. No. 3,726,059, Ser. No. 204,450, filed on Dec. 3, 1971 now abandoned and Ser. No. 195,619 filed on Nov. 4, 197 l now US. Pat. No. 3,719,022 all by the instant inventors, and made herein of reference.

SUMMARY OF THE INVENTION It is, therefore the main object of the present invention to provide improvements which are equally suitable to the devices for direct stuffing and to the devices where the netting is pre-gathered about the extrusion cylinder of the apparatus.

In general, the above-mentioned known devices employ a stuffing tubular element which is rigidly. connected to the direct-stuffing device or, alternately, removably connected to the device using the gathering technique. In either method and respective apparatus, the device is provided with mechanical gathering means which may be either of the continuousoperation type or of the reciprocating type. These netgathering mechanical means are, in turn, provided with net-seizing jaw-like means and, due to their continuous or reciprocating movement, gather the netting about the tubular extruding element, unwinding said netting from a spool or other suitable feeding source. To effect such gathering of the netting, the extruder is provided with a terminal portion thereof which is connected to the body of the extruder through a constriction wherein are located the means for aligning and holding in position the extruder tube.

One purpose of the present invention consists insubstituting, at least in part, the. pivots, heretofore known, with driving rolls, so that the holding and aligning operations may be coordinated directly with the auxiliary operation of unwinding of the netting, thus preventing possible jamming and rendering the overall operation of the device more regular. The speed of these rolls, hereinafter defined as an auxiliary unwinding rolls, is proportional to the operational speed of the netgathering means, so that the unwinding of the netting from the feed roll or spool is proportional to the drag rate of the netting by the gathering means, or, respectively, to the rate or cycle of operation of these means.

Generally, therefore, there is provided a kinematic linkage directly between the gathering means for the netting and the auxiliary unwinding rolls thereof, said rolls, as explained hereabove, also serving the purpose of holding the extruder in place and preventing longitudinal displacements thereof.

In accordance with the present invention, the auxiliary unwinding rolls, further, cooperate with winding counter-rolls supported by the terminal portion of the extruding element; this cooperation facilitates even further the unwinding of the netting.

Another feature of the invention resides in that, when the extruding tubular element is removable, this can be supported by an external tubular sheath which brings the terminal section thereof and the constriction into engagement with the auxiliary unwinding rolls. The removable, internally located tubular element has a frusto-conical opening facing in the opposite direction from the terminal section of the sheath. As the netting is being gathered on the removable tubular element, there occurs an action by the netting on this frustoconical opening such that the removable tubular element is expelled from the tubular sheath to a point where the frusto-conical opening contacts a microswitch which arrests the net-gathering action.

Still another feature of the invention resides in that, when the device is provided with net-gathering means which operate reciprocatingly, there are employed, in lieu of the known jaw gathering means, shoes with a cylindrical surface and capable of acting on the netting by pressure, when the carrier is moving in one direction, while disengaging completely from said netting, when the carriers moving in the opposite direction. The actionof these cylindrical shoes will therefore permit the reciprocating gathering of the netting in cooperation with the displacement to-and-fro of the carrier. Each shoe is supported by a pin, the axis of which is convergent with the axis of the tubular extruding element on which the netting is gathered. The shoe is freely slidable on the supporting pin against the action of a spring and the converging direction of the pin coincides with the direction of displacement of the carrier when effecting a return movement. In this manner, the shoe will approach the tubular element during the netgathering movement of the carrier and, conversely, be farthest located from the tubular element during the opposite movement of the carrier.

In accordance with a variant of the invention, the shoe is supported by a rod which is radially positioned with respect to the net-supporting tubular element and provided with a double-link pitman which, by means of a suitable spring, causes the engagement and disengagement of the shoe with and from the netting, respectively, in cooperation with the displacement of the carrier in one direction or in the other.

THE DRAWINGS The present invention will become more apparent from the following detailed description thereof and from the accompanying drawings, in which:

FIG. 1 is an elevational view of the device of the invention as applied to direct-stuffing apparatus;

FIG. 2 is a frontal view of the device of FIG. 1 taken in the direction of arrows IIII;

FIG. 3 is a top planar view of the device of FIG. 1;

FIG. 4 is a sectional view taken along the line IVIV of FIG. 3;

FIG. 5 is a sectional view taken axially along the line V-V of FIG. 3;

FIG. 6 is an elevational view of another embodiment of the device of the invention;

FIG. 7 is a frontal view of the device of FIG. 6 taken in the direction of arrows VII-VII;

FIG. 8 is a top planar view of the device of FIG. 6;

FIG. 9 is a schematic elevational view, partly in crosssection, showing in detail the auxiliary unwinding rolls of the device of the invention;

FIG. 10 is a sectional view of FIG. 9 taken along the line X-X thereof;

FIG. 11 is an elevational view similar to FIG. 9 and showing the application of rolls to the device of the invention;

FIG. 12 is a sectional view of FIG. 11 taken along the line XII-XII thereof;

FIGS. 13, 14 and 15 are side elevational, front elevational and top planar views, respectively, of the device of the invention applicable to an apparatus wherein the net-gathering is effected upon a removably connected tubular extruder;

FIGS. 16, 17 and 18 are side elevational, front elevational and top planar views, respectively, of a variant embodiment of the device of the invention;

FIG. 19 is a schematic, longitudinally cross-sectional view showing in detail the auxiliary unwinding rolls of the device of the invention, as applied to a netgathering apparatus having a removable tubular extruder and using particular netting designs;

FIG. 20 is an elevational view showing in detail a variant of the net-gathering shoes as applied to an apparatus provided with reciprocating net-gathering means;

FIG. 21 is an elevational sectional view of FIG. 20 taken along the line XXIXXI;

FIG. 22 is a top planar view of FIG. 20;

FIG. 23 is an exploded sectional view of a detail of FIG. 20;

FIG. 24 is a sectional view of FIG. 23 taken along the line XXIVXXIV;

FIG. 25 is an elevational view, similar to FIG. 20, showing another variant of the net-gathering shoes;

FIG. 26 is an elevational sectional view of FIG. 25 taken along the line XXVI-XXVI;

FIG. 27 is a top planar view of FIG. 25;

FIG. 28 is an exploded sectional view of a detail of FIG. 25; and

FIG. 29 is a sectional view of FIG. 28 taken along the line XXIXXXIX.

DETAILED DESCRIPTION OF THE INVENTION With reference now to FIGS. 1-5 of the accompanying drawings, the device for the direct stuffing of foodstuff into tubular netting is composed of the following structural elements: a rigid frame 1 with vertical uprights 2 and 3 therein. These uprights carry the horizontal sliding guides 4 for the net-gathering carrier indicated generally at 5. The uprights 2 carry, further more, a group of four rolls 6 mounted in pairs on the extremity of the bifurcated supports 7 and 8 which serve the function of holding in position and alignment of the immobile stuffing tubular element or tube indicated generally at 9.

Tube 9, preferably of metal, is provided with a feed inlet 9a near which act the centering and positioning rolls 6. Inlet 9a is aligned with a small frame 10 which slidably supports a blade 11 by which the foodstuff 12 is fed within tube 9. Furthermore, tubular element 9 is provided with a terminal section 9b which is rigidly connected to the rest of the tube by means of a constriction 13 in correspondence to which act additional positioning and centering rolls 14. These rolls 14 are rotatably supported on the uprights 3.

Rolls 14 serve furthermore the additional function of unwinding the netting 15 to permit it to be gradually gathered on the tubular element 9 by the reciprocating movement of the carrier 5.

Carrier 5, by means of a mechanical arrangement which comprises a pitman 16 and a connecting line 17, is reciprocatingly displaced by a motor 18 along the sliding guides 4 in such a fashion that a pair of jaw means 19, carried on the carrier itself, gather at each displacement in the positive or net-gathering direction a quantity of netting commensurate to the length of said positive displacement. This net-gathering is effected in the vicinity of the feed inlet 9a of the tubular element. The jaw means 19, during the positive displacement of the carrier, drag the netting unwinding it from a suitable spool (not shown). The netting slides onto the terminal section 9b of the tubular element and such sliding action is aided by the controlled rotation of rolls 14. To this purpose, the rolls 14 derive the reciprocating movement of the carrier 5 by means of a return chain 20 which is trained about sprocket 21 (carried on the shaft of one of said rolls l4) and also trained about a return idle pinion. Chain 20 is fixed at one point thereof to the carrier 5 of the device so that when the carrier reciprocates, so does the chain 20 thereby causing the sprocket 21 to reciprocate. A pair of gears 21b connects, furthermore, rolls 14 mutually to one another and, since their peripheral velocity is equal to the drag velocity of the netting, the rolls effect their auxiliary net-dragging action preventing, at the same time, the net from becoming jammed or overstretched and possibly broken.

The device of the invention is furthermore provided with detecting means which sense the presence of netting gathered in correspondence with a reference line positioned in the proximity of the feed inlet 9a and are capable of interrupting the displacement of the carrier 5 whenever the region 15a of the gathered netting has reached such reference line. These detecting means preferably consist of a photo electric cell 22 which cooperates with a screen 23 supported by a rigid arm connected to the carrier 5, so as to force the screen 23 to follow the displacements of the carrier 5. The photo electric cell 22 sees" the amount of netting gathered in correspondence of the reference line, when the screen 23 is displaced therefrom by the carrier 5, and sends a signal to arrest the carrier. Severing means 24 are positioned intermediate the feed inlet of the tubular element and the frame 10 and serves the purpose of cutting the netting 15 after the stuffing operation has terminated.

The device is, furthermore, provided with a pneumatic system of expulsion of the foodstuff introduced in the tubular element. To this purpose, (see FIG. 5),

the tube is provided with a piston 25 which freely slides therein. In correspondence with the blind extremity of the tubular element there is an opening 26 cooperating with a nozzle 27 for the injection of compressed air. When the foodstuff 12 is introduced in the tubular element, the piston 25 is displaced toward the blind end of the tube 9 incorrespondence with the location of the opening 26. To expel the foodstuff, the nozzle 27 is brought into contact with opening 26 into which compressed air is injected. The nozzle is' supported by an oscillating yoke 28 controlled by a pull rod 29 in cooperation with a pedal 30. By acting upon the pedal, the nozzle is set in oscillating motion and brought into contact with the opening 26, as described hereabove, and a source of compressed air (not shown) is activated by means of a microswitch 31 associated with the yoke 28.

The variant of FIGS. 6-8 of the accompanying drawings refers to a stuffing device of the type hereabove described (direct stuffing), which however employs different means for gathering of the netting. In these figures, wherein similar elements are represented by similar reference numerals, the sliding carrier 5 is replaced by mechanical means 32 subdivided into two groups positioned diametrically opposite to each other on the tubular element 9, intermediate the extremities thereof. The two groups 32-32a are capable of axial displacement with respect to the tubular element 9, so as to obtain the desired gathering of the netting 15. The members of each group 32, 32a are mounted on respective support chains 33, 33a, each chain engaging a corresponding toothed group of pinions 34-34a of which at least one is a driving pinion. The motion is achieved by employing transmission shafts 35, 36 which receive their motion directly from the shaft of the moving rolls 14 via the conical couples 37 and 38, respectively. To the shaft of roll 14 is connected motor 18 and a reducing gear 39 is located therebetween the motor and the shaft. In the arrangement hereabove described, the rolls l4 retain their auxiliary action of unwinding the netting from the spool or feeder. To aid in this, it is advantageous to associated with the rolls 14 the idle counter-rolls as indicated at 40 and 41 of FIG. 9. These counter-rolls are positioned tangentially to the rolls l4 and are supported by the terminal portion 9b of the tubular element 9.

In FIG. 10, it can be readily seen that, by employing the counter-rolls, the constriction 13 between the tube 9 and its terminal portion 9b is provided, advantageously, with a section with flat and parallel faces, as indicated at S. It should, however, be pointed out that the positioning of rolls 14, eventually cooperating with the counter-rolls 40-41 as mentioned above, is not limited. In a device for stuffing of foodstuff in accordance with the invention, the rolls 14 may be replaced by holding pins as shown at 6a in FIGS. 11 and 12. In these figures, it can be seen that the holding and centering pins are supported two-by-two by the corresponding forks 7-8 to engage the circular constriction 13-which connects the tube 9 with its terminal section 9b.

FIGS. 13-15 of the accompanying drawings refer to a device of the type described hereabove, but restricted to the gathering of an amount of netting greater than one single length of stufiing. Also in this case the device may be provided with a net-gathering carrier 5 with drag jaws 19 capable of reciprocating movement and with auxiliary unwinding rolls .14 operatively associated with a motor 18. Conversely, the device may be constructed as shown in the variants of FIGS. 16-18, wherein instead of the sliding carrier 5, the netgathering means employed are of the type shown at 32, 32a and described in connection with FIGS. 6-8. In either device, illustrated respectively in FIGS. 13-15 and 16-18, the device is provided with an external sheath as at 9 and having a terminal section 9b separated by a constriction 13 on which act the net-dragging rolls 14. Within the sheath 9', as mentioned earlier, there is located a removable tubular element 42 provided with a frustoconical opening 42a which protrudes beyond the sheath 9'. Tube 42 is supported within the surrounding sheath 9 and externally thereto by a bracket 45 with a frusto-conical plug 45a which bracket 45 slides on guides 46.

In operation, the device works as follows:

A quantity of netting is gathered by the drag jaws 19 or, alternately, by the members 32 to the extermity of the immobile sheath 9'. From this extremity, the netting is reversed onto the tubular element 42. As the gathering action proceeds, the tube 42 is slid from the sheath 9, thus pushing the sliding carrier 45 until the latter reaches the end of its displacement and actuates a microswitch 47 to arrest the movement of the netgathering means. In this position, the tubular element 42 is completely expelled from the sheath 9' and can be removed together with the netting gathered thereon after having severed the end of the netting by means of cutting means 24.

FIG. 19 illustrates a variant of the arrangement hereabove described. It relates to the gathering of netting made of rhombic mesh, or the like, which is susceptible of nonuniform stretching. According to this variant, the tubular element 42 is supported within-the surrounding sheath 9 by an axial spine 43 having intermediate spaced annular elements 44. The axial spine 43 is in turn supported by a terminal support 48 provided with at least one base bar 49 telescopically sliding within a guide 50 which is rigidly fixed to the frame I of the apparatus. The terminal support 48 is provided with a microswitch 51 cooperating with the frusto-conical feed inlet 42a of the tubular element 42. In this arrangement, also, the tube 42 is expelled from the sheath 9 by thenet-g athering action and, reached its maximum expulsion, causes by means of the microswitch 51 the stoppage of the net-gathering means. From this maximum extension position, the tube 42 can be removed by sliding the bar 49 within the guide 50, so as to remove the spine 43 from the sheath 9. Here also there are provided the cutting means (not shown) for severing the netting at the extremity of the tubular element 42 and permit the complete removal thereof.

FIGS. 20-24 refer to another variant suitable for devices having net-gathering means provided with reciprocating motion. According to this variant, the sliding carrier 5 is provided with shoes 52 (instead of jaws l9) capable of engaging a larger quantity of netting and of preventing possible damage thereto. As shown in FIGS. 20-24, there are provided three shoes 52 positioned at from one another. Each shoe is comprised of a cylindrical block of plastic material or the like and is provided with an appendix 53 which has an opening therein for the passage of the holding means carried by the carrier. These holding means preferably consist of a pin 54 for each shoe and bent so as to show a lower horizontal portion 544 with its axis convergent with the axis of the tube 9. On this portion 54a slides the appendix 53 of the shoe against the action of a spring 55, which spring tends to push the shoe in engaging contact with the netting 15.

As it is evident from the drawings, the arrangement is such that, as the carrier slides in the net-gathering direction, the shoes 52 are caused to contact the netting and to gather it. Conversely, as the carrier slides in the opposite direction, the shoes will disengage from the netting and remain idle while the carrier completes the displacement.

If the supports 54 are employed as illustrated in the drawings, it is advantageous to have the vertical portion of such supports seated within the cylindrical seat 56 and retained therein by fastener 57. This arrangement is such as to allow a radial control of the position of each shoe with respect to the tube 9.

Finally, FIGS. 25-29 of the drawings illustrate still another variant with respect to the mode of connecting each shoe 52 to its respective support 54. in accordance with this variant, the support consists of the single vertical portion 54 of the pin, said portion 54 being contained slidably within seat 56 and being herein withheld by the fastener 57. To the extremity of each vertical rod there is movably connected the shoe 52, a double-link pitman 58 being interposed between the shoe and the vertical rod. The support 54 is also provided with a finger 59 on which acts a spring 60 to push the shoe radially into engagement with the surface of the tube 9. The opcration of this structural arrangement is equivalent to the one described in detail hereinabove: each shoe 52 is actuated into contact engagement with tube 9 during each positive displacement of the carrier and, conversely, actuated into disengagement from said tube 9 during the negative displacement of the carrier 5. Obviously, the details of execution of the operation and of the various structural elements of the device may be altered and varied without in the least exiting from the principles and scopes of the present invention.

'What we claim and wish to secure by letters Patent of the United States is:

1. In a semi-automatic device for stuffing foodstuff into tubular netting and for gathering continuously said tubular netting, on stuffing tubular elements, the improvement comprising, in combination, a stuffing tubular element; means for introducing and pneumatically expelling foodstuff from said tubular element; mechanical means for gathering of said netting onto said tubular element, means for holding and positioning said tubular element and for concurrently unwinding said netting during said gathering; said holding and positioning means being kinematically connected to said gathering means for synchronized operation thereof; driving means for said gathering means and said holding and positioning means; and means for detecting the presence of said netting onto said tubular element and controlling said driving means.

2. The improvement according to claim 1, wherein said tubular element is immobile.

3. The improvement according to claim 1, wherein said tubular element is removably supported within a tubular sheath surrounding it; and wherein said sheath is acted upon by centering, aligning, net-unwinding rolls; and wherein said tubular element is expelled from said sheath by the gathering action of said netting.

4. The improvement according to claim 3, wherein said removable tubular element is provided with a frusto-conical terminal upon which acts said netting for expelling, when gathered, said tubular element from said sheath.

5. The improvement according to claim 4, wherein said tubular element is supported externally t0 and in corresponding of said frusto-conical terminal by a carrier slidably displaceable on supporting guides, and wherein the sliding displacement of said carrier is arrested by microswitching means.

6. The improvement according to claim 3, wherein said removable tubular element is centered within said sheath by means of an axial spine having a plurality of spaced annuli intermediate the ends thereof, and wherein said spine is in turn supported by a sliding terminal supporting means.

7. The improvement according to claim 1, wherein said net-gathering means are reciprocating means.

8. The improvement according to claim 1, wherein said net-gathering means are continuously-operating means.

9. The improvement according to claim 1, wherein said holding and positioning means comprise a plurality of driving rolls; and wherein said tubular element is provided in correspondence of said rolls with a constriction section; said rolls deriving their motion from said net-gathering means by means of a combination chain-pinion-sprock'et.

10. The improvement according to claim 9, wherein said driving rolls cooperate with a plurality of counterrolls carried on said tubular element and sheath.

11. The improvement according to claim 1, wherein said net-gathering means includes a sliding carrier capable of reciprocating motion and carrying netdragging means which are engaging said netting only during the displacement of the carrier in one single direction.

12. The improvement according to claim 11, wherein said net-dragging means are composed of a plurality of shoes having a cylindrical surface and acting on said netting by exerting a differential pressure thereon.

13. The improvement according to claim 12, wherein said shoes are supported by means of a pin the axis of which is convergent with the axis of said tubular element; and wherein said shoes are freely sliding against the action of a spring and the direction of convergence of said pin coincides with the direction of return sliding of said carrier.

14. The improvement according to claim 12, wherein said shoes are supported by rods radially positioned with respect to said tubular element; and wherein a double-link pitman is interposed between each shoe and each radial rod, said pitman being actuated by a spring to cause the engagement and disengagement of said shoe in its radial displacements.

15. The improvement according to claim 12, wherein said net-gathering means are means supported by a continuously moving chains actuated by a shaft provided for the said rolls. 

1. In a semi-automatic device for stuffing foodstuff into tubular netting and for gathering continuously said tubular netting, on stuffing tubular elements, the improvement comprising, in combination, a stuffing tubular element; means for introducing and pneumatically expelling foodstuff from said tubular element; mechanical means for gathering of said netting onto said tubular element, means for holding and positioning said tubular element and for concurrently unwinding said netting during said gathering; said holding and positioning means being kinematically connected to said gathering means for synchronized operation thereof; driving means for said gathering means and said holding and positioning means; and means for detecting the presence of said netting onto said tubular element and controlling said driving means.
 2. The improvement according to claim 1, wherein said tubular element is immobile.
 3. The improvement according to claim 1, wherein said tubular element is removably supported within a tubular sheath surrounding it; and wherein said sheath is acted upon by centering, aligning, net-unwinding rolls; and wherein said tubular element is expelled from said sheath by the gathering action of said netting.
 4. The improvement according to claim 3, wherein said removable tubular element is provided with a frusto-conical terminal upon which acts said netting for expelling, when gathered, said tubular element from said sheath.
 5. The improvement according to claim 4, wherein said tubular element is supported externally to and in corresponding of said frusto-conical terminal by a carrier slidably displaceable on supporting guides, and wherein the sliding displacement of said carrier is arrested by microswitching means.
 6. The improvement according to claim 3, wherein said removable tubular element is centered within said sheath by means of an axial spine having a plurality of spaced annuli intermediate the ends thereof, and wherein said spine is in turn supported by a sliding terminal supporting means.
 7. The improvement according to claim 1, wherein said net-gathering means are reciprocating means.
 8. The improvement according to claim 1, wherein said net-gathering means are continuously-operating means.
 9. The improvement according to claim 1, wherein said holding and positioning means comprise a plurality of driving rolls; and wherein said tubular element is provided in correspondence of said rolls with a constriction section; said rolls deriving their motion from said net-gathering means by means of a combination chain-pinion-sprocket.
 10. The improvement according to claim 9, wherein said driving rolls cooperate with a plurality of counter-rolls carried on said tubular element and sheath.
 11. The improvement according to claim 1, wherein said net-gathering means includes a sliding carrier capable of reciprocating motion and carrying net-dragging means which are engaging said netting only during the displacement of the carrier in one single direction.
 12. The improvement according to claim 11, wherein said net-dragging means are composed of a plurality of shoes having a cylindrical surface and acting on said netting by exerting a differential pressure thereon.
 13. The improvement according to claim 12, wherein said shoes are supported by means of a pin the axis of which is convergent with the axis of said tubular element; and wherein said shoes are freely sliding against the action of a spring and the direction of convergence of said pin coincides with the direction of return sliding of said carrier.
 14. The improvement according to claim 12, wherein said shoes are supported by rods radially positioned with respect to said tubular element; and wherein a double-link pitman is interposed between each shoe and each radial rod, said pitman being actuated by a spring to cause the engagEment and disengagement of said shoe in its radial displacements.
 15. The improvement according to claim 12, wherein said net-gathering means are means supported by a continuously moving chains actuated by a shaft provided for the said rolls. 